The invention is based on a method and fuel injection system for operating an internal combustion engine. Such a method is realized in known fuel injection systems in which the fuel to be injected is available in a high-pressure fuel reservoir. Then however the danger is that because the fuel is constantly available at high pressure, if the fuel injection valve or its electrical triggering fails, then the fuel injection valve following fuel injection will remain in the open position, so that fuel will continue to be introduced constantly at high pressure into the applicable combustion chamber of the engine. In the ensuing compression stroke, this quantity of fuel may ignite abruptly together with the reintroduced fresh air. This leads to considerable heat production, associated with an extreme increase in pressure, one that is not contemplated for normal engine operation and thus can lead to the destruction of the engine.